Ahearn (Eocene of the United States)

Where: Pennington and Shannon County, South Dakota (43.6° N, 102.5° W: paleocoordinates 44.9° N, 93.6° W)

• coordinate based on political unit

When: Ahearn Member (Chadron Formation), Chadronian (37.2 - 33.9 Ma)

Environment/lithology: terrestrial

Primary reference: J. Clark and J. R. Beerbower. 1967. Geology, paleoecology, and paleoclimatology of the Chadron Formation. Fieldiana 5(5):21-74 [J. Alroy/J. Alroy/J. Alroy]more details

Purpose of describing collection: paleoecologic analysis

PaleoDB collection 16885: authorized by John Alroy, entered by John Alroy on 18.02.1993, edited by Jonathan Marcot

Creative Commons license: CC BY (attribution)

Taxonomic list

• dated at 36.3 +/- 0.7, 35.1, and 36.2 Ma: Emry et al. 1987; average is 35.87 (= 36.80) Ma
 Salientia - Pelobatidae
Eopelobates grandis Zweifel 1956 spadefoot toad
 Testudines - Trionychidae
"Apalone leucopotamica" = Trionyx leucopotamicus5
"Apalone leucopotamica" = Trionyx leucopotamicus5 Cope 1891 softshell turtle
 Testudines - Carettochelyidae
Anosteirinae indet.5 Lydekker 1889 turtle
"Pseudanosteira or Anosteira... scrap"
 Testudines - Panemydidae
Emydidae indet.2 Rafinesque 1815 turtle
 Crocodylia - Alligatoridae
Alligator cf. prenasalis Loomis 1904 alligator
 Squamata -
Peltosaurus sp. Cope 1872 squamates
 Rodentia - Eomyidae
Eomyidae indet. Winge 1887 rodent
 Rodentia - Ischyromyidae
Ischyromys sp. Leidy 1856 rodent
 Perissodactyla - Brontotheriidae
Brontotheriidae indet.1 Marsh 1873 brontothere
 Perissodactyla - Hyracodontidae
Hyracodon cf. priscidens Lambe 1905 odd-toed ungulate
probably OK in light of Prothero 1996e
 Perissodactyla - Rhinocerotidae
Subhyracodon mitis1 Cope 1875 rhinoceros
Trigonias sp. Lucas 1900 rhinoceros
 Perissodactyla - Tapiridae
Colodon occidentalis Leidy 1868 tapir
 Perissodactyla - Equidae
Mesohippus bairdi1 Leidy 1850 anchitheriine horse
 Carnivora - Ursidae
Parictis gilpini n. sp.3 Clark and Guensburg 1972 bear
Little Corral Draw, Pennington Co.
Parictis parvus n. sp. Clark and Beerbower 1967 bear
from west flank of Quinn Draw, Shannon Co.: see Clark and Guensburg 1972
Parictis dakotensis3 Clark 1936 bear
SE 1/4 NE 14 NW 1/4 sec 5 T4S R12E, Pennington Co.; same as type locality of P. gilpini
 Carnivora - Amphicyonidae
Brachyrhynchocyon dodgei1 Scott 1898 bear-dog
 Carnivora - Nimravidae
? Eusmilus sp. Gervais 1876 false sabre-tooth
 Ungulata - Merycoidodontidae
Miniochoerus cf. forsythae8 Schultz and Falkenbach 1968 oreodont
one specimen of "Merycoidodon sp."; said to to "probably" be this species
Merycoidodon sp. Leidy 1848 oreodont
"Big Corral Draw... Pennington Co.:" discussed by Stevens and Stevens 1996
 Ungulata - Tayassuidae
Perchoerus minor7 Cook 1922 peccary
 Ungulata - Entelodontidae
Archaeotherium cf. coarctatum Cope 1889 even-toed ungulate
Archaeotherium cf. mortoni Leidy 1850 even-toed ungulate
"Archaeotherium cf. altidens" = Scaptohyus altidens1 Sinclair 1922 even-toed ungulate
 Ungulata - Tylopoda
Tylopoda indet. even-toed ungulate
"camelid new genus and species": may be Montanatylopus; specimens not discussed by Prothero 1986
 Ungulata - Camelidae
Poebrotherium sp.1 Leidy 1847 camel
 Ungulata - Agriochoeridae
Agriochoerus cf. antiquus Leidy 1850 agriochoerid
 Ungulata - Anthracotheriidae
Anthracotheriidae indet.6 Leidy 1869 anthracothere
 Ungulata - Protoceratidae
Pseudoprotoceras longinaris4 Cook 1934 protoceratid
 Ungulata - Hypertragulidae
Hypertragulidae indet. Cope 1879 ruminant
 Hyaenodonta - Hyaenodontidae
Hyaenodon cf. montanus Douglass 1902 eutherian
Hyaenodon cf. horridus Leidy 1853 eutherian